Current leakage techniques for radio frequency instruments

This application claims the benefit of priority to U.S. Provisional Patent Application Ser. No. 63/092,925, filed Oct. 16, 2020, the contents of which are hereby incorporated by reference in their entirety.

The present invention relates to medical procedure instruments and, more particularly to techniques for detecting current leakage of radio frequency (RF) instruments.

Medical instruments can include electrodes and drivers for delivering RF energy to an anatomical target. The RF energy can provide a variety of medical benefits. As with most instruments, or tools, time can affect the efficiency of delivering the benefit of the tool. For example, repeated use or exposure to various elements can degrade the efficiency of the instrument. For RF instruments, one aspect of the instrument that is not immune to degradation is the insulation of the conductor(s) coupling the RF energy source with the RF electrodes.

Techniques for detecting leakage current of an electrosurgical instrument are provided. In an example, a method of operating an electrosurgical instrument can include applying a therapy signal to electrode conductors of the electrosurgical instrument, determining leakage current of an leakage conductor coupled to the electrosurgical instrument exceeds a first threshold, and providing a first indication in response to the determining the leakage current of the leakage conductor exceeds the first threshold.

This section is intended to provide an overview of subject matter of the present patent application. It is not intended to provide an exclusive or exhaustive explanation of the invention. The detailed description is included to provide further information about the present patent application.

1 FIG. 100 101 102 103 101 104 105 106 104 102 107 103 102 103 101 102 illustrates generally an example systemaccording to the present subject matter. The system can include an RF instrument, an energy sourceor electrosurgical unit (ESU), and an optional footswitch. The RF instrumentcan include a handle, a shaft, and an end-effector. The handlecan be connected with the energy sourcethrough a cable. The footswitch, which can be a hand switch in some examples, can be connected with the energy source. In certain examples, when an end-user operates a pedal of the footswitch, the turning on/off of the supply of energy to the RF instrumentfrom the energy sourceis controlled. For example, when the pedal is pressed, an output is produced based on a state where radio-frequency energy is appropriately set. When the pedal is released, an output of the radio-frequency energy is stopped.

104 105 104 107 104 105 107 106 104 106 106 105 104 105 106 106 106 104 102 105 101 102 105 105 105 In certain examples, the handlecan be formed into a shape that can be easily grasped by an operator. The shaftis arranged on one end of the handle. The cablecan extend from the one end of the handlecoaxially with the shaft. The cablecan include a number of conductors for conducting RF signals to one or more RF electrodes mounted to the end effector. The handlecan include one or more handle levers for controlling the orientation or actuation of the end effector. In some examples, the end effectorcan include a single electrode (not shown) extending from the end of the shaft. In some examples, one or more levers of the handlecan allow for the electrode to be extended and retracted relative to the end of the shaft. In some examples, a lever can allow for the electrode to be rotated or hinged. In some examples, the end effectorcan include two electrodes (not shown) with a first electrode mounted on a first jaw of the end-effectorand a second electrode mounted on a second jaw of the end-effector. In such an example, and in addition to functions discussed above with respect to a single electrode end-effector, a lever of the handlecan allow for the two electrodes to be brought together and separated in a motion akin to a pliers or scissors. In some examples, only one of the jaws may be moveable. During a procedure, the one or more electrodes can be brought into proximity to an anatomical target by the operator. Upon location at a desired position, the operator can then initiate the ESUto provide a signal to the electrodes and RF energy can be applied to the anatomical target. As discussed below, the shaftof the RF instrument, among other things, protects conductors connecting the electrodes with the ESU. Over time, the insulation of the conductors can begin to deteriorate, and an increasing portion of the energy, via leakage current, intended to be distributed by the electrodes can leak via leakage current of the RF signal conducted via the shaft. If the leakage current is above a certain level, RF energy may be applied to tissue adjacent the shaftand may cause patient discomfort. In addition, since some energy intended for the one or more electrodes leaks via the shaft, the intended procedure can take longer or can be completed using additional wasteful energy. The present inventors have recognized techniques to detect leakage current and modify operator procedures if certain levels of leakage current are detected.

2 FIG. 200 200 201 202 201 205 206 210 211 207 201 202 206 205 206 206 201 illustrates a simplified view of an example systemto show details of the example leakage current detection. The systemincludes a RF instrumentand an RF energy source. The RF instrumentcan include a shaftthat can extend from a handle (not shown), end effector, electrodes,, and a multiple conductor cableelectrically connecting aspects of the RF instrumentto the RF energy source. In certain examples, the end effectorcan be mechanically coupled with the shaft. The end effectorcan be used to cut tissue, cauterize tissue, heat tissue, etc. In some examples, the end effectorcan include a single electrode. In some examples, the RF instrumentcan include more than two electrodes.

207 205 205 205 205 207 205 205 205 202 210 211 210 211 205 205 The multiple conductor cablecan include a conductor for each electrode, electrode conductors (+, −), and a leakage conductor (Ø) configured to electrically couple to the shaft. In certain examples, the shaft, or portions of the shaftcan be electrically conductive. In some examples, the shaftcan be hollow or can form a channel. The conductors (+, −, Ø) of the multiple conductor cablecan extend with the shaftand, in some examples, can extend within or coaxially with a hollow shaft, or within a channel of the shaft. The electrode conductors (+, −) can extend to the electrodes, and during operation can conduct the electrical RF signals of the RF power sourceto the electrodes (+, −) to generate the RF energy at and about the electrodes,. The electrode conductors (+, −) can include an exterior layer to insulate the electrode conductors (+, −) from radiating the electrical RF signals except at or about the electrodes,. However, after repeated use and with age, the exterior layer of the electrode conductors (+, −) can deteriorate. The deterioration can be attributed to age, environment, movement, such as movement during use, or combinations thereof. The deterioration of the exterior layer of the electrode conductors can allow RF energy, manifested as leakage current, to be conducted via the shaftor conductive portions of the shaft.

205 200 As discussed above, the leakage conductor (Ø) can electrically couple a leakage detection circuit with the shaft. The leakage conductor (Ø) can direct leakage current to the leakage detection circuit and, in some examples, can direct leakage RF energy away from tissue not intended to be exposed to RF energy. The leakage detection circuit can measure the leakage current or can compare a level of the leakage current to one or more thresholds to determine whether the leakage current is high enough to inhibit further application of RF energy or to raise an alarm to indicate the leakage current is approaching a level requiring maintenance of the system.

3 FIG. 300 300 301 302 301 305 306 310 311 307 301 302 306 305 306 306 301 illustrates a simplified view of an example systemto show details of the example leakage current detection. The systemincludes a RF instrumentand an RF energy source. The RF instrumentcan include a shaftthat can extend from a handle (not shown), end effector, electrodes,, and a multiple conductor cableelectrically connecting aspects of the RF instrumentto the RF energy source. In certain examples, the end effectorcan be mechanically coupled with the shaft. The end effectorcan be used to cut tissue, cauterize tissue, heat tissue, etc. In some examples, the end effectorcan include a single electrode. In some examples, the RF instrumentcan include more than two electrodes.

307 306 312 313 306 307 305 305 305 302 310 311 310 311 305 306 312 313 306 The multiple conductor cablecan include a conductor for each electrode, electrode conductors (+, −), and a leakage conductor (Ø) configured to electrically couple to a component of the end effector, such as a hinge pinor conductive portionof a jaw of the end effector. The conductors (+, −, Ø) of the multiple conductor cablecan extend with the shaftand, in some examples, can extend within or coaxially with a hollow shaft, or within a channel of the shaft. The electrode conductors (+, −) can extend to the electrodes, and during operation can conduct the electrical RF signals of the RF power sourceto the electrodes (+, −) to generate the RF energy at and about the electrodes,. The electrode conductors (+, −) can include an exterior layer to insulate the electrode conductors (+, −) from radiating the electrical RF signals except at or about the electrodes,. However, after repeated use and with age, the exterior layer of the electrode conductors (+, −) can deteriorate. The deterioration can be attributed to age, environment, movement, such as movement during use, or combinations thereof. The deterioration of the exterior layer of the electrode conductors can allow RF energy, manifested as leakage current, to be conducted via conductive portions of the shaft, conductive portions of the end effectorsuch as a hinge pin, or other conductive componentsof a jaw of the end effectorthat are not intended to pass the RF energy.

312 313 306 300 As discussed above, the leakage conductor (Ø) can electrically couple a leakage detection circuit with the hinge pinor other conductive componentsof a jaw of the end effector. The leakage conductor (Ø) can direct leakage current to the leakage detection circuit and, in some examples, can direct leakage RF energy away from tissue not intended to be exposed to RF energy. The leakage detection circuit can measure the leakage current or can compare a level of the leakage current to one or more thresholds to determine whether the leakage current is high enough to inhibit further application of RF energy or to raise an alarm to indicate the leakage current is approaching a level requiring maintenance of the system.

4 FIG. 402 405 410 411 410 411 415 420 402 420 431 430 410 411 430 405 illustrates generally an electrical model of a system including an example leakage current detector. The system can include an RF instrument and a ESU. Only certain elements of the RF instrument related to the present subject matter are shown such as a shaft, electrodes,, and conductors (+, −, Ø). In operation, the electrodes,can be brought into proximity or into contact with tissueto complete an RF circuit and allow RF energy to be applied to a patient for therapeutic procedures. The RF energy can be generated at the ESU. The ESUcan include an RF generator, a controller, and a leakage current detector. The RF generator can be electrically coupled to the electrodes,via first and second electrode conductors (+, −). A third electrical conductor, or wire, a leakage conductor (Ø), can couple the leakage current detectorto components of the RF instrument thru which leakage current may travel should insulation of one of the electrode conductors be damaged, deteriorate or break. One such component of the RF instrument, among others, can be the shaft.

5 FIG. 2 205 FIG., 1 105 FIG., 530 530 531 532 533 534 535 531 illustrates generally an example leakage current detection circuit. The leakage current detection circuitcan communicate with a controllersuch as the controller of an ESU. The leakage current detection circuit can receive the leakage conductor (Ø) from the shaft (e.g.,;). In certain examples the leakage current detection circuit can include a sense resistor, a fault detection circuitand a controller interface. In some examples, the leakage current detector can include a switchto selective couple the leakage conductor (Ø) with the sense resistor, for example, in response to a first state of a test command signal from the controller. In certain examples, in response to a second state of the test command signal, the leakage conductor (Ø) can be coupled directly to ground.

533 536 536 532 538 538 533 537 536 537 534 531 537 FLT The fault detection circuitcan include a comparator. The comparatorcan compare a sense voltage developed by any leakage current across the sense resistorto a fault reference. If the sense voltage becomes higher than the fault reference (REF), the output of the comparator can become active to indicate a fault leakage current condition. In some examples, the controller can coordinate sensing the fault leakage current condition, or lack thereof, with the test command signal. In certain examples, the controller can conduct a leakage current detection test while providing an RF signal to the electrodes. In some examples, the RF signal can be an RF test signal that is not intended to provide substantial therapy but can still provide an indication of leakage current during therapeutic application of RF energy. In some examples, the controller can conduct a leakage current test just before application of therapeutic RF energy. If, during the leakage current test, a fault leakage current condition is indicated, the use of the RF instrument can be terminated. In certain examples, a fault leakage current condition can occur and can last a very short duration. In some examples, the fault detection circuitcan include a latchto detect an active state of the output of the comparatorand latch the fault leakage current condition. The output (FAULT) of the latchcan be provided to the controller via the controller interface. In response to a reset command from the controller, the latchcan be reset to release the fault leakage current condition.

530 539 539 540 540 532 542 542 540 531 531 539 541 540 541 531 534 531 541 ALM In some examples, the leakage current detection circuitcan include an optional alarm detection circuit. The alarm detection circuitcan include an alarm comparator. The alarm comparatorcan compare a sense voltage developed by any leakage current across the sense resistorto an alarm reference (REF). If the sense voltage becomes higher than the alarm reference, the output of the alarm comparatorcan become active to indicate an alarm leakage current condition (ALARM). In some examples, the controllercan coordinate sensing the alarm leakage current condition, or lack thereof, with the test command signal. In certain examples, the controllercan conduct a leakage current detection test while providing an RF signal to the electrodes. In some examples, the RF signal can be an RF test signal that is not intended to provide substantial therapy but can still provide an indication of leakage current during therapeutic application of RF energy. In some examples, the controller can conduct a leakage current test just before application of therapeutic RF energy. If, during the leakage current test, an alarm leakage current condition is indicated, the use of the RF instrument can be terminated. In certain examples, an alarm leakage current condition can occur and can last a very short duration. In some examples, the alarm detection circuitcan include a latchto detect an active state of the output of the alarm comparatorand can latch the alarm leakage current condition. The output (ALARM) of the latchcan be provided to the controllervia the controller interface. In response to a reset command from the controller, the alarm latchcan be reset to release the alarm leakage current condition.

FLT ALM FLT ALM 538 542 538 542 331 In certain examples, the fault reference (REF), the alarm reference (REF), or the fault reference (REF)and the alarm reference (REF)can be set via the controller. In certain examples, the alarm reference and the fault reference may be referred to individually as a threshold or a current limit.

6 FIG. 600 601 603 605 illustrates generally an example methodof operating an electrosurgical instrument. At, an RF signal can be applied to electrode conductors of the electrosurgical instrument. The RF signal can be generated by an RF generator coupled to a controller such as a controller of an ESU. In some examples, the RF signal can be for applying therapy. In some examples, the RF signal can be a test signal. At, a leakage current detector can determine whether leakage current of a leakage conductor exceeds a threshold. The leakage conductor can be coupled to components of the electrosurgical instrument that are not designed to provide therapeutic RF energy to a patient and where the capture of leakage current can indicate an electrode conductor has broken, been damaged or has deteriorated to a point of needing repair. Such components can include, but are not limited to metal components such as a shaft of the electrosurgical instrument or linkage components for actuation of one or more jaws. At, in response to determining excessive leakage current based on the threshold, an indication can be generated by the leakage current detector. In certain examples, the indication can inhibit further generation or delivery of RF energy from the ESU. In some examples, the leakage current detector can include two thresholds for comparison to the detected leakage current of the leakage conductor. A first threshold can be an alarm threshold to provide an early indication of leakage current exceeding the alarm threshold. The early indication may not inhibit further operation of the ESU but may need to be reset in order to apply subsequent electrosurgical therapy. The second threshold can be a fault threshold and can provide a more persistent indication compared to the alarm indication. The fault indication may terminate generation of RF signals and can inhibit operation of the RF generator until the fault is cleared via a maintenance operation of the ESU of the electrosurgical instrument.

The above detailed description includes references to the accompanying drawings, which form a part of the detailed description. The drawings show, by way of illustration, specific embodiments in which the invention can be practiced. These embodiments are also referred to herein as “examples.” Such examples can include elements in addition to those shown or described. However, the present inventors also contemplate examples in which only those elements shown or described are provided. Moreover, the present inventors also contemplate examples using any combination or permutation of those elements shown or described (or one or more aspects thereof), either with respect to a particular example (or one or more aspects thereof), or with respect to other examples (or one or more aspects thereof) shown or described herein.

In the event of inconsistent usages between this document and any documents so incorporated by reference, the usage in this document controls.

In this document, the terms “a” or “an” are used, as is common in patent documents, to include one or more than one, independent of any other instances or usages of “at least one” or “one or more.” In this document, the term “or” is used to refer to a nonexclusive or, such that “A or B” includes “A but not B,” “B but not A,” and “A and B,” unless otherwise indicated. In this document, the terms “including” and “in which” are used as the plain-English equivalents of the respective terms “comprising” and “wherein.” Also, the terms “including” and “comprising” are open-ended, that is, a system, device, article, composition, formulation, or process that includes elements in addition to those listed after such a term are still deemed to fall within the scope of subject matter discussed. Moreover, such as may appear in a claim, the terms “first,” “second,” and “third,” etc. are used merely as labels, and are not intended to impose numerical requirements on their objects.

The above description is intended to be illustrative, and not restrictive. For example, the above-described examples (or one or more aspects thereof) may be used in combination with each other. Other embodiments can be used, such as by one of ordinary skill in the art upon reviewing the above description. The Abstract is provided to comply with 37 C.F.R. § 1.72(b), to allow the reader to quickly ascertain the nature of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of a claim. Also, in the above Detailed Description, various features may be grouped together to streamline the disclosure. This should not be interpreted as intending that an unclaimed disclosed feature is essential to any claim. Rather, inventive subject matter may lie in less than all features of a particular disclosed embodiment. The following aspects are hereby incorporated into the Detailed Description as examples or embodiments, with each aspect standing on its own as a separate embodiment, and it is contemplated that such embodiments can be combined with each other in various combinations or permutations.